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Glama

lob

by io.usefulapi

Send a letter (COSTS MONEY)

lob_create_letter
Destructive

⚠️ SENDS A REAL LETTER and charges your Lob account (use a test_ key to avoid real mail/charges). to/from accept an address id (adr_…) or inline object. file accepts an HTML string, a hosted PDF/URL, or a template id (tmpl_…). color is required. Cancelable only before send_date. Lob API: POST /v1/letters.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
toYesEither an existing address id (adr_…) or an inline address object.
fileYesLetter body: HTML string, asset/PDF URL, or template id (tmpl_…).
fromYesReturn address (id or inline object). Required for letters.
colorYestrue = color printing, false = black & white.
send_dateNoISO-8601 date/time to schedule the send (future). Cancelable until then.
descriptionNoInternal label.
double_sidedNoPrint on both sides. Default true.
merge_variablesNoKey/value data merged into HTML templates.
address_placementNoWhere the recipient address is placed.

TDQS

A4.2/5.0
Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

The description adds important behavioral context beyond the destructiveHint annotation: it warns about real charges, explains that test keys avoid real mail, and mentions cancelability. No contradictions with annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is very concise: three sentences with no fluff. Key information is front-loaded with the warning emoji, and technical details are efficiently presented with backticks.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool has 9 parameters and no output schema, the description provides a solid overview: cost, test key, cancelability, parameter types, required fields. It does not list all optional parameters but the schema handles that. Leaves no major gaps for agent decision-making.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the description's parameter notes (e.g., `to`/`from` accept id or inline object) are redundant. It does not add new meaning beyond the schema, so baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states 'SENDS A REAL LETTER' which is a specific verb and resource. It also highlights the cost and test key usage, differentiating it from sibling tools like lob_create_postcard. The title further reinforces the purpose.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Provides some guidelines: use a test_ key to avoid real charges, and cancelable only before send_date. However, it does not explicitly compare to sibling tools or state when to use this tool over alternatives like lob_create_postcard.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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TDQS

A3.9/5.0
Disambiguation5/5

Every tool targets a distinct resource and action, with clear verb-noun names like create_address and verify_us_address. There is no overlapping functionality, and even similar operations (e.g., list for different resources) are distinct.

Naming Consistency5/5

All tools share the 'lob_' prefix and follow a consistent verb_noun pattern (e.g., create_postcard, list_letters, verify_intl_address). Multi-word nouns use underscores, maintaining uniformity throughout.

Tool Count5/5

With 18 tools, the set covers the primary mail fulfillment operations—address management, postcards, letters, checks, self-mailers, and address verification—without feeling bloated or sparse. The count is well-suited to the domain.

Completeness2/5

The tool set has notable gaps: no create_check or create_self_mailer, no cancel for letters or checks despite being referenced, no update/delete for addresses, and only list for templates. These missing operations will likely cause agent failures in common workflows.

Resources